1. Field of the Invention
The invention relates to a device and a method for signalling in connection with runways. The device and the method are intended to give pilots of aircraft, helicopters etc. information especially at night and in case of poor visibility about the borders of a runway, doors, traffic regulations and the like.
2. Prior-Art
When using known methods for this kind of signalling, use is in most cases made of devices with signal means such as light signs and signal lights. The latter are, for instance, signal lights of different colors showing the approach lane of the airport as well as the beginning, edges and end of the runway. The signal means are supplied with current and controlled in their functions by means of cables and other electric equipment. The signal means and the associated equipment in the device are expensive to purchase, install and maintain. For instance, in international relief work, it is sometimes necessary to use airfields, the ordinary signalling device of which has been destroyed or does not exist at all. An emergency device must then be sent to the airfield and installed to enable the field to be used also when the visibility is not optimal. Since such a device is heavy and bulky, it requires great freight capacity in relief consignments. Moreover, much more work is necessary for the installation.
Technical Problem
The object of the invention is to provide a method and a device, both mentioned in the introduction, for signalling at runways, The device should:
be simple and inexpensive to buy, install and maintain
allow quick installation in an emergency airfield or an airfield with its ordinary signalling device destroyed
be light and require little space to allow quick transportation to the location of use
consume a small amount of power to make it possible to use small power plants.
This object is achieved by the device and the method being given the characteristic features that appear from a signalling device for placement adjacent to a runway comprising an essentially permanent sheet-shaped structure with two opposite boundary surfaces fixed in an orientation relative to the runway. The signal means is sheet-shaped with two opposite boundary surfaces and comprises a structure material of color pigment adapted to reflect light in a visible area and, on the other hand, pigment of a wavelength-converting material, is adapted to emit, from an activating radiation, visible light of approximately the same as the reflected light from the color pigments. The signal means is arranged in such a manner that if at least part of an arbitrarily selected boundary surface are illuminated by the activating radiation, corresponding parts of the other boundary surface will emit the visible light emitted by the wavelength-converting material.
Also, the color pigment of the signal means and its pigment of the wavelength-converting material are jointly or each are separately contained in the signal means in one or more of the following ways: mixed into a matrix included in the polymer material, applied to one boundary surface, and applied to both boundary surfaces.
The signal means is arranged as a flat screen, and the screen is arranged vertically and perpendicularly to the longitudinal direction of the runway.
Alternatively, the signal means is made of a flexible material and adapted, when located adjacent to the runway, to be expanded to the permanent shape by a support. Two poles are arranged vertically adjacent to the runway, and the signal means is adapted to be expanded to a flat screen between the poles. The signal means is arranged to be in omnidirectional, for instance, by being made as a tube which can be closed at the upper end, or the signal means is adapted to be expanded by the support to a dimensionally stable, possibly truncated, cone.
A lighting device is provided and comprises a source of radiation for activating radiation. The source of radiation is adapted to illuminate a plurality of signal means simultaneously, and a first and a second signal means, as well as a first and a second source of radiation is provided, each illuminating the two signal means. The signal means and the sources of radiation being arranged such that if the distance between the first source of radiation and the first signal means is greater than the distance between the first source of radiation and the second signal means, the distance between the second source of radiation and the first signal means is to be smaller than between said second source of radiation and the second signal means.
In the device, the structure material is a polymer material and the active radiation is UV light. The pigment of a wavelength-converting material is a fluorescent material.
An activating radiation is allowed to illuminate one of the boundary surfaces of the signal means and is converted into of a different wavelength, which from the boundary surface of the signal means is shown with a predetermined color to a flying observer. The activating radiation is normally invisible to the observer, and that the converted radiation is visible to him. The signal means is illuminated from two directions , in case of flat signal means both towards its front and towards its back.
According to the invention it is suggested that the individual signal means, for instance, those used to show the borders of the runway, be supplied with energy by being illuminated by some radiation of a form of energy that preferably cannot be perceived by the pilots to prevent them from being disturbed by the radiation. The signal means convert in their turn this radiation energy to radiation that can be perceived by the pilots. In the preferred embodiment, use is made of UV light from e.g. UV lamps as energy radiators. Normally this light cannot be perceived by pilots. However, by letting the signal means contain a fluorescent material, these means can convert the UV light into visible light. Depending on what material the signal means contain, the signal means can be made to emit different signal colors. Instead of UV light, IR light can be used. This light would then be converted into light having a shorter wavelength by the signal means so as to make it perceivable.
If it is desirable that the signal means emit radiation that is to be perceived by the own pilots only, it is possible to use, for instance, UV light or IR light which can be converted into light having a longer or shorter wavelength that can be perceived only by those pilots who are equipped with appropriate visual instruments.
The signal means could in fact contain a fluorescent material that is non-translucent, but according to the invention a translucent material is preferred that allows the energy radiators illumination to pass. This results in the advantages that an object acting as signal means can emit light also from a side that is not directly illuminated from the front and that radiation to some extent can penetrate means and reach other signal means shaded by these means.
The signal means should be sheet-shaped with two opposite boundary surfaces and comprise a polymer material and on the one hand common color pigment which is adapted to reflect light in the visible area and, on the other hand, pigment of a wavelength-converting material, e.g. a fluorescent material, which is adapted to emit, from an activating radiation, such as UV light, visible light of approximately the same color as said reflected light from the color pigments. Moreover, the signal means should be arranged in such a manner that if at least parts of an arbitrarily selected boundary surface are illuminated by said activating radiation, corresponding parts of the boundary surface will emit the visible light emitted by the wavelength-converting material.
The color pigment of the signal means and its pigment of the wavelength-converting material should jointly or each separately be contained in the signal means, for instance, in one or more of the following ways: mixed into a matrix included in the polymer material, applied to one boundary surface and applied to both boundary surfaces. According to the selected amounts of the different types of pigment for a certain volume of the matrix, the properties of these pigments and the original translucency of the matrix, the signal means will, in certain light and other radiation conditions, emit and let through different amounts of reflected light and converted light, respectively. The correct composition for a predetermined purpose can only be obtained by testing different alternatives.
As material contained in the signal means, a rigid material, such as rigid plastic panels, can be used. For an easily transported device, however, it is preferred that the signal means be made of a flexible sheet-shaped material which can be a fiber material, such as a fabric cloth or a plastic-coated cloth, but which in the embodiment, for reasons of cost and production, has been chosen to be a plastic sheeting which can be fiber-reinforced. In the manufacture of this plastic sheeting, use can be made of a plastic, e.g. styrene, ethylene or PVC plastic, which is translucent to radiation of wavelengths within a wide range. Into this basic material, on the one hand common color pigments giving the sheeting a certain color in daylight that is reflected and penetrated by radiation and, on the other hand, pigments of a fluorescent material which gives a converted light that preferably has approximately the same color as the above-mentioned daylight color of the sheeting.
Plastic sheeting of the above-mentioned type is, depending on its quality, penetratable by UV and similar radiation to different degrees. From this point of view, the thickness of the sheeting in the thicknesses involved is insignificant. The dimensioning should therefore be effected on the basis of the mechanical stress to which the sheeting will be subjected. The thickness of the sheeting is to be selected, inter alia, with respect to the material and size of the signal means and its exposure to currents from the drive means of aircrafts. A thickness of 0.25-0.5 mm is usually sufficient for the PVC material of the preferred embodiment.
For a piece of limp plastic sheeting to be able to act as signal means, it should be given a flat surface of a certain minimum see. It should be arranged such that the normal of the surface is directed as far as possible towards an intended viewer. The greater the deviation from this angle, the smaller amount of light intensity reaches the viewer. The signal means of the invention should therefore have an essentially invariable, permanent shape and, in any case, for e.g. the screens of the preferred embodiment have an invariable, permanent orientation in relation to the runway, such that its character is not changed unintentionally. These requirements can be satisfied by the piece of sheeting being held expanded in a support which is designed and arranged in such manner that the piece of sheeting is correctly oriented.
On runways for aircraft it is common to have signal means in rows along the long sides of the field, The pieces of sheeting, which suitably are of square or rectangular shape, are there held preferably vertically expanded transversely of the longitudinal direction of the runway, such that their surfaces point at an approaching aircraft coming from one or the other direction in the longitudinal direction of the runway. It is possible to use as a support for each signal means a frame fixed in the ground or two parallel poles which are vertically fixed in the ground and are approximately of the same height and In which the comers of the piece of sheeting are fixed by means of e.g. rubber bands which are stretched straight outwards, By inclining the tips of the parallel poles, for example, towards the end of the runway, or changing their position in relation to the longitudinal direction of the runway, the light character of the signal means can be changed.
With a view to guiding pilots of helicopters, the signal means should, however, be omnidirectional and can then be designed as a cylinder, possibly with a closed upper end. The piece of sheeting can then be formed to a sector or a part of a circular ring, whose straight edges are joined. It is kept expanded by means of e.g. a wire frame similar to that in a lampshade to form a tone or a truncated cone, which is preferably straight, circular and vertical, like in the preferred embodiment. The frame that should allow good penetration by radiation, can comprise a pole stuck into the ground and a round ring in which the circular lower edge of the piece of sheeting is clamped. The signal means will produce radiation also against the light by the fact that activating radiation penetrates parts of the signal means that are facing the source of radiation and the inner space of the signal means, whereupon the radiation activates part of the signal means on the other side of this space, which emit the wavelength-inverted light For radiation of this kind of signal means, weak sources of radiation can be placed in the same.
In connection with runways for aircraft, the flat signal means, the screens, are arranged, inter alia, at the long sides of the runway and directed perpendicular to these sides. For short runways, 6-10 yellow or white signal means are used on each side. According to an embodiment of the invention, it is suggested that an energy radiator, such as a UV lamp, be allowed to illuminate a number of the converting signal means of the invention, in this case, for instance, 6-10, which consequently will each emit a signal light. This gives the advantage that only the single UV lamp requires electric equipment, not each of the 6-10 signal means as in prior-art technique. This means that a large part of the electric equipment, such as lamp fittings, cables and the like as well as the installation thereof can be excluded. In certain cases, it may be convenient to divide the function of the energy radiator between two energy radiators, such as two UV lamps like in the preferred embodiment. If these are combined to a unit or placed close to each other, the installation work does not increase significantly.
For all means to have the same luminous intensity although the transfer of energy decreases with the distance, it is further suggested that the number of signal means be illuminated from at least two positions located outside the area of the positioning of this number. The location of the positions is preferably such that if the distance between a first of these positions and a first signal means in the number is greater than the distance between the same position and a second signal means in the number, the distance between the second of these positions and the first signal means should be smaller than between this position and the second signal means. As a result, the reduction of the received energy from e.g. one UV lamp between two signal means will, owing to a longer distance to this lamp, be compensated for by an increase of the received energy from the other UV lamp owing to a smaller distance to this lamp.
Now assume that fluorescent signal means arranged in a row, for instance, the above-mentioned at the edge of the runway, are illuminated by two UV searchlights which have the same luminous intensity and which are arranged outside the to ends of the row. If the searchlights have such radiation characters that their luminous intensity decreases approximately linearly with the distance, all the signal means will receive in total the same effect and, consequently, have the same luminous intensity.
When using flat signal means, screens, it is most natural for the two searchlights to each illuminate one side of the screens, and to be positioned close to the extensions of the rows since the energy received by the means is at its maximum when the radiation occurs perpendicular to the sides. Moreover, the searchlights can then have narrow beams of light, which minimizes the power consumption. This kind of illumination can, of course, also be used in omnidirectional signal means.
It has been found that the above-mentioned translucent fluorescent signal means are highly effective also in daylight even if they are not illuminated by special energy radiators such as UV lamps. Especially when the sun is low in the morning and evening hours of the day, pilots must notice signal means against the bright light. They will then be blinded and will have difficulties in noticing prior-art signal means. With the inventive signal means, especially the fluorescent flat screens or cones, the UV light in sunlight, which illuminates the screens from behind, will cause fluorescence which is directed towards the pilots and which preferably is arranged to have the daylight color of the screen. This light considerably reinforces the visible light coming from the sun""s illumination of the rear of the screen which is translucent also to daylight. Consequently, the screens will stand out sharply against the background and will be easy for the pilots to discover. It goes without saying that the effect is pronounced even if there is no opposite light and the sun illuminates the front of the screen, although not to the same pronounced degree. Also in this daylight case a converted light is obtained, whose activating radiation is invisible to the viewer. This light certainly just adds to the otherwise obtained light from the sun, but the UV light that exists in the sunlight is invisible to the viewer and does not contribute to making it difficult for the viewer to notice the signal means.
Only monochromatic means have been described above, However, a signal means can have a plurality of different colors. It may comprise multicolored fields, for instance, be divided into vertical red and yellow strips or exhibit a symbol or a character.
Advantages
With the invention, simple methods and means for signalling in runways are provided. The cost of a device and the installation thereof becomes much lower than for prior-art devices. If used as an emergency device, it can be transported and installed much more quickly since it has a much lower weight and requires less complicated electric arrangements, such as portable power plants, since the power consumption can be reduced to a considerable extent. This is due not only to the fact that a smaller number of energy supplying units are used, but also to the fact that since the surface of the signal means of the invention is much larger, this requires a smaller amount of totally emitted power to be observed. According to calculations, the cost of simple devices can be reduced to {fraction (1/20)} and the power consumption to ⅕. The installation is much simpler than for prior-art devices, among other things, because about 2 km of electric wiring in airfields of the size shown in the preferred embodiment can be avoided.
In private airfields, the signal means of the invention can be installed without any energy radiators such as UV searchlights. Signal means, which are inexpensive and effective in the morning and in the evening as well as in case of haze and reduced visibility for other reasons, will be obtained at a low cost,